1. Field of the Invention
This invention relates to a method of forming ball cores and more particularly to a method of forming ball cores of thermoplastic material.
2. Description of the Prior Art
Baseballs, as are used in the United States by professional leagues and little leagues, are formed of a cork or rubber core wound with wool yarn and cotton thread, and covered with a stitched, two-piece leather cover. In some instances the cover may be vinyl or rubber, especially in the little leagues where the durability of practice balls is essential. Consequently, the density of the baseball along with its attendant properties is determined by its materials of construction and by how tightly the wool yarn is wound. Therefore, there are variables in baseball manufacturing which are not capable of adequate control and baseball manufacturers have endeavored to find materials of construction sufficient to provide consistency to their product.
Softballs such as are used in both slow and fast pitch softball leagues are manufactured in various dimensions with a vast range of physical properties. One common design uses a cork or kapok core wound with synthetic yarn or thread with a cover formed upon the surface of the softball much the same as a baseball. Participants in softball leagues have desired to have a softball of constant properties to provide consistency to their game.
Also, a major factor in the production of both baseballs and softballs is cost since the winding of cores involves substantial labor costs or investment in winding machines.
Confronted with the problem of a uniform product along with increasing labor and capital costs, ball manufacturers endeavored to form ball cores of plastic material to solve both of these problems. Exemplary of such efforts are the teachings of U.S. Pat. No. 3,976,295 and Canadian Patent No. 632,220. However, as in any sport, participants therein and distributors of such equipment are reluctant to change from existing equipment, and therefore, balls intended to replace the conventional baseball have had minimal acceptance. Although there has been some success in various sports fields with plastic equipment, exemplified by U.S. Pat. No. 3,268,636 and 3,313,545, the lack of success in the baseball and softball area is attributed to factors such as a difference between the playing properties of the conventional ball and the proposed replacement balls. One such property, which is particularly important, is the sound which is produced when the ball is hit by the bat.
Thus, in accordance with the present invention, baseballs and softballs are manufactured which have substantially the same physical properties as conventional balls, including sound when struck. Further, the balls have uniform properties and are produced economically.